A split gasket is one that is of a circumferential dimension sufficient for it to completely encircle a pipe, the entire gasket having only two ends which are brought into compressive relation with each other upon tightening down of the segmented pipe coupling.
Gasket segments more usually are equal in number to the number of coupling segments, usually two, each of which has two ends for compressive engagement by a corresponding end of a juxtaposed gasket segment. Segmented pipe couplings are well known in the art, and are employed either for connecting the adjacent ends of a pair of pipes to each other in sealed relationship, or, for connecting the end of a single pipe to some other structure in sealed relationship.
In the former instance, the segmented pipe coupling incorporates g single split gasket, or plural gasket segments formed from an elastomeric material and which are received within the respective coupling segments. The gasket or the respective gasket segments are provided with dual sealing lips for engagement with the outer periphery of the respective pipes.
In the latter instance, the respective segments each include a radial flange for attachment to the said other structure, the gasket or gasket segments providing the required seal at the interface of the flange and the other structure, and also providing a sealing lip for engagement with the outer periphery of the pipe.
It has been prior proposed in De Raymond U.S. Pat. No. 4,678,208 to provide a gasket segment which is of greater circumferential length than the circumferential length of the coupling segment in which it is to be received, such that the adjacent ends of a pair of such gasket segments engage each other prior to final tightening down of the pipe coupling, and exert both circumferential and radially inward compressive stresses on the gasket segments at their ends to force them into intimate sealing engagement with the outer periphery of the associated pipe as the segmented pipe coupling is tightened down. De Raymond teaches the provision of abutments at the respective ends of the gasket segments to limit movements of the gasket segments to the end thereof under compressive loading.
This, however, entails sliding frictional movement of the ends of the gasket segments relative to the pipe exteriors when the coupling segments are applied to the pipe, and in turn carries with it the requirement that a lubricant be applied to the inner circumferential face of the respective gaskets prior to the assembly of the segmented pipe coupling onto the pipe.
The lubricant is required in order to minimize scuffing and abrasion of the gasket segments as they are applied to the pipe and during tightening down of the coupling, and also, to facilitate movements and displacements within the body of the gasket segments as required to ensure correct seating and fluid tightness of the gaskets, particularly at the opposite ends thereof.
Scuffing or abrasion of the gasket segments can result in the formation of crumbs abraded from the gasket material, and which interfere with the proper seating of the gasket segments in fluid fight relation with the juxtaposed outer surface of the associated pipe.
This requirement to lubricate the gasket segments is inconvenient, in that it must be done immediately prior to assembly of the segmented pipe coupling onto the pipes, which itself is possibly being assembled onto pipes positioned in highly inconvenient locations.